=m+n+m-n=2m
=m+n-(m-n) = m+n-m+n = 2n
2) + =2a²+2b²
=a²+2ab+b²-(a²-2ab+b²)=a²+2ab+b²-a²+2ab-b²=4ab
3)+=5x²-5x+4-4x²+5x-4=х²
-=5х²-5х+4+4х²-5х+4=9х²-10х+8
y = 10/(x - 2) + 6; y - 6 = 10/(x - 2); x - 2 = 10/(y - 6); x = 10/(y - 6) + 2
(m-5)(m+5)-(m+4)(m-4)=m^2-5^2-(m^2-4^2)=m^2-25-m^2+16=-25+16=-9